1. Technical Field
The present invention relates to a cooling-type switching element module, and, in particular, to a structure for causing a coolant to flow so as to cool switching elements.
2. Related Art
Electric-powered vehicles that travel using a motor generator, such as hybrid electric vehicles and electric vehicles, are widely used. Typically, an electric-powered vehicle incorporates an electric power conversion circuit that converts electric power between a motor generator and a secondary battery. The electric power conversion circuit includes, for example, a step-up/step-down converter for converting a voltage, and an inverter for converting direct current electric power to alternating current electric power.
Switching elements used in the electric power conversion circuit generate heat in response to switching operations. The electric power conversion circuit is therefore provided with a cooler for the switching elements. The cooler includes, for example, heat dissipation fins provided with channels through which a coolant flows. Typically, the greater the volume of the channels, the better the cooling performance. As such, when the cooling performance is improved, the cooler may be larger sized. Also, an inductance component included in a wiring conductor of the electric power conversion circuit may increase in magnitude depending on the arrangement of the switching elements. In consideration that such an inductance component may cause a surge voltage in the electric power conversion circuit and its surrounding electric circuits, the design and manufacturing costs for a high withstand voltage may increase. Further, when direct current electric power is converted to polyphase alternating current electric power, variations in electric constants may occur among phases depending on the arrangement of the switching elements, resulting in situations in which an alternating current voltage and an alternating current become unstable; for example, phase voltages and phase currents become nonuniform, or the neutral point potential varies. To address these problems, techniques such as those described in patent publications JP 2002-26215 A, JP 2004-297846 A, JP 2001-128467 A, and JP 2007-116840 A are being devised.
JP 2002-26215 A discloses a cooling fluid cooling-type semiconductor device. This device includes a plurality of flat cooling tubes and a plurality of semiconductor modules that are arranged in parallel. Each of the semiconductor modules is interposed in a gap between adjacent flat cooling tubes. This publication describes that cooling performance is improved by pinching two flat cooling tubes between which a semiconductor module is interposed, by means of a U-shaped spring component.
JP 2004-297846 A discloses an electric power conversion device including a cooler. This electric power conversion device is used for a motor, and the cooler is arranged around a drive shaft of the motor. An electric power semiconductor module for supplying electric power to the motor is attached on a cooling surface of the cooler. This publication describes that the above-described structure downsizes the electric power conversion device.
JP 2001-128467 A discloses an electric power conversion device that uses an intelligent power module (IPM). This electric power conversion device has an insulator interposed between a flat plate conductor connected to a positive electrode terminal of the IPM and a flat plate conductor connected to a negative electrode terminal of the IPM to form a smoothing capacitor between the positive electrode terminal and the negative electrode terminal. This publication describes that the above-described smoothing capacitor prevents a surging voltage from occurring in the circuit.
JP 2007-116840 A discloses an inverter module. In this inverter module, a plurality of insulating substrates on which switching elements are mounted are arranged in a circumferential direction at predetermined intervals with respect to the center axis of a cylindrical housing. Conductors connected to the insulating substrates are arranged within the plurality of insulating substrates. This publication describes that the above-described structure makes the lengths of the conductors equal, and downsizes the inverter module.